Press for dewatering slurries



Sept. 15, 1959 v c. w. znzs 2,903,960

PRESS FOR DEWATERING SLURRIES Filed June 27, 1957 INVENTOR. 0M4 W 2156 United States Patent PRESS FOR DEWATERING SLURRIES ,Carl W. Zies, Lakewood, Ohio, assignor to International Basic Economy Corporation, New York, N.Y., a corporation of New York Application June 27, 1957, Serial No. 668,368

1 Claim. (Cl. 100-448) This invention relates to novel and improved press means for dewatering slurries, and particularly slurries of low consistency, namely in which the percentage of solid material is relatively low. The invention is especially applicable to the removal of water from wood pulp slurries having less than ,ten percent of solid content.

Presses of the rotating screw type have heretofore been used to remove a certain amount of liquid from wood pulp slurries. .One such press which has been widely used commercially is sold under the trade name Expeller. It is capable of exerting high pressure. The material is advanced by screw pressure through an enclosing barrel, the walls of the barrel having narrow slotted openings between barrel bars to permit escape of the liquid, while retaining the solid material which is discharged from the barrel end. While up to the present time this has been one of the best practical solutions to the dewatering problem, there are certain attendant disadvantages. Slurries of low consistency are not dewatered with satisfactory efliciency because the solid material is driven into the barrel bar interstices and blocks them. Some of the solid material escapes with the liquid. The press efliciency decreases as the process proceeds because of the reduced liquid escape capacity. The Expeller type of press therefore operates more efliciently with consistencies in excess of about twenty-five percent solids, and the art has been searching for dewatering means which efficiently and economically removes a desired percentage of liquid from low consistency slurries.

An object of the present invention is to provide means for partially dewatering slurries containing less than about ten percent solids.

Another object of the invention is to provide relatively low pressure helical screw means for removing a preliminary increment of liquid from a low consistency slurry.

Another object of the invention is to provide a screw press of the character defined in the last two preceding paragraphs which has a high material-moving capacity per unit of time.

Another object of the invention is to provide a screw press of the nature defined in the last three preceding paragraphs which has a relatively large drainage area.

Another object of the invention is to provide a press of the nature defined in the last four preceding paragraphs in which the pressure build-up within the barrel is automatically limited by reason of the novel structure of the helical screw means.

Another object of the invention is to provide a screw press of the general nature hereinabove briefly defined, which can be constructed easily and economically, and which can be operated with a relatively low power expenditure.

Other objects and advantages will be apparent from a study of the following description, in conjunction with the accompanying drawings of one embodiment, in which:

Fig. 1 is a vertical sectional view taken axially through 2,903,960 Patented Sept. 15, 1 9 59 2 a dewatering press constructed in accordance with the principles of my invention.

Fig. 2 is a vertical sectional view taken transversely of the press barrel at approximately the position of the line 2-2 of Fig. 1.

It will be understood that the apparatus shown in Figs. 1 and 2 is merely one exemplification embodying the invention, and that its description in connection with the dewatering of wood pulp slurries is not intended to indicate that the invention is limited only to this field, since it will be immediately apparent that the invention has other potential practical applications.

In the drawings there is shown an elongated cylinder 20 supported on cross walls 21a, 21b, 21c rising from a base 22, there being side walls 23 (Fig. 2) which provide, with the base, a trough to receive water and discharge it through an outlet fitting 24. Any intermediate wall has an opening 25 at the bottom to permit water to flow to the discharge port and fitting 24.

I have shown the cylinder 20 supported on semicircular cut-outs on the supporting walls, such as on the cradle .26 on wall 21]). This auxiliary supporting structure can take any suitable form, since not a necessary part of the present invention.

Running axially through the cylinder is a shaft 27 sup- Ported at its e S n in a 1 1 .2 in the le port on .204 and at its right end in a bearing 29 carried on a column 30 on base 22.

Shaft 27 carries a helical screw 33 which extends through the major portion of the cylinder. The portion 33a of screw 33 near the shaft is of rigid metallic composition. The portion 33b of the screw adjacent to the cylinder wall is formed from a flexible material such as natural or synthetic rubber or some other yieldable composition. This flexible part is bonded to the metallic root portion by any suitable recognized method.

Part 33b has a wiping fit against the inner peripheral wall of cylinder 20. Although yieldable when it meets positive resistance, the rubber helix is sufliciently sturdy to normally urge a fluent slurry towards the right end of the cylinder. Water or other liquid escapes. through the multitude of apertures 34 in the cylindrical wall and drops into the drain trough as hereinabove noted.

The right end of cylinder 20 is provided with a choke closure 35 which is slidable on the shaft 27 and is held in place by a spring 36 upon which compressive tension is applied by an adjustable backing nut 37 which can be advanced or withdrawn by reason of its threaded engagement with the shaft. Other effective biasing means could be provided, such as an adjustably counterweighted abutment.

The shaft is rotated by a motor 38 through a gear reducing assembly 39 or in any other convenient way.

Operation of the unit show in the drawings as follows: Motor 38 is energized to rotateshaft 27 in the correct direction to advance material from left to right in Fig. 1, the slurry being poured into the receiving chute portion 20a and travelling in the direction of the arrows. Tension on spring 36 is adjusted to permit normal screw pressure to open choke 35 while maintaining suflicient pressure on the slurry material to squeeze out the desired amount of liquid, the higher consistency residue falling into chamber 40 whence it can be removed in any suitable way. The helical screw decreases in pitch towards the right end to compensate for volumetric shrinkage resulting from escape of liquid through perforations 34. The flexible portion 33b of the screw wipes loose solid particles or fibers from the inner peripheral barrel wall leaving the barrel perforations free to permit drainage. Any pressure in excess of a pre-calculated amount will cause the flexible portion of the helical screw to deflect to any degree required, thus permitting automatic adjustment to accommodate variation in slurry consistencies, and variations in the rate of feed to the press. These flexible flights prevent formation of a solid plug which would cause serious overloading of the motor and wide variations in the consistency of the discharged fibers when wood pulp is being dewatered.

Referring to the apparatus just disclosed as a slurry press, it can be manufactured at a small fraction of the cost of the prior heavy duty fiber presses used in the art. These former fiber presses had a relatively low capacity when operating on pulps having consistencies of less than about fifteen percent, and more especially less than six percent. The economic value of the present slurry press is particularly evident when it is used in a preliminary way, namely to process a slurry having a consistency of less than about fifteen percent, so as to increase that consistency to higher than fifteen percent, at which point the heavy duty fiber press can take over efliciently. Many of the pulp slurries encountered in paper making plants have a consistency as low as three percent. My slurry press is designed to increase the consistency of pulp slurry to the neighborhood of twenty-five percent at which point a press of the Expeller type can take over efliciently.

7 "What I claim is:

Apparatus for the removal of unwanted liquid from a solid-liquid slurry comprising an elongated cylindrical stantial escape of solids, a rotatable shaft extending axially through the cylinder, helical screw means fixedly carried on said shaft and adapted, when rotated, to advance said slurry through said cylinder from said inlet end toward said outlet end, said screw means having a root portion of non-flexible material and a crest portion of yieldable material, said crest portion extending from said root portion for a distance of at least one-half of the diameter of the screw means to provide flexible flights, the outer peripheral edge of said flights having wiping contact with the inner peripheral wall of the cylinder, said screw means varying progressively in pitch from said inlet end toward said outlet end, and an adjustable choke yieldably biased to a position tending to close said outlet end, whereby a predetermined pressure may be maintained on a slurry advanced through said cylinder to squeeze the desired amount of liquid therefrom, and any pressure in excess of said predetermined pressure will cause said flexible flight portion to deflect for accommodating variations in slurry-consistencies.

References Cited in the file of this patent UNITED STATES PATENTS 643,891 Bussells Feb. 20, 1900 714,174 Guy Nov. 25, 1902 2,397,305 Wheat Mar. 26, 1946 FOREIGN PATENTS 592,834 Great Britain Sept. 30, 1947 

